Water level responsive controls for combustion apparatus



3 Sheets-Sheet l ySept. 10, 1957 M. w. sToUT WATER 4LEVEL. RESPONSIVECONTROLS FOR COMBUSTION FFRA'IUS Filed May 1, 1953 INVENToR MmqrW StoutBY m4,

his ATTORNEY .Hmmm

Sept. '10, 1957 M. w. srou'r 2,805,652

WATER LEVEL RESPONSIVE CONTROLE RoR ooMBUsTroN APRARA'rus Filed May 1,1953 `SASheelLS-Sheet 2 iai/l I Fig. 2.

INVENTOR BVE E. his ATTORNEY.

Minor-'W Stout Sept. l0, 1957 M. w. sTOLUVT 'A 172,805,652

WATER LEVEL REsPoNsIvEcoN-TRQLS FORV CQMBUSTIONAPPARATUS j Filed May 1,1955 v 1 INVENTOR C Minarmsfwt y United States Patentv 2,805,652Patented Sept. 10, 1957 hfice WATERLEVEL RESPONSIVE CONTROLS FORCOMBUSTION APPARATUS Minor W. Stout, Webster Groves, Mo. ApplicatiorrMay1, 1953, Serial No. 352,500 V1- Claim. (Cl. 122-448) This inventionrelates to improvements in controls for combustion apparatus. Moreparticularly this invention relates to improvements in controls thateration of combustion apparatus.

It is therefore an object of the presenti invention lo provide animproved control that assures safe operation of combustion apparatus.

Most boilers have indicators or controls that respond to the level ofthe water in the boiler. Where the controls are automatic, it isessential that the' controls do not become 'stuck in a position thatindicates a full supply of water for the boiler at a time when thatsupply is insuflicient. If this were to happen, the flame in the` boilercould readily destroy the met-al walls-.of the boiler. Where theoperators of the boiler regularly flush out the boiler and keep it freeof sludge, the controls usually work.

However, it is known that the operators of' boilers areA not as regularin` their cleaning of the boilers as -they could be and that sludgeaccumulates in a great number of boilers. That sludge can interferewiththe operation of thelow water controls and cause them tofstick in a1position which indicates a full supply of water in the boiler eventhough the supply of water is low. This is dangerously objectionable.The present invention obviates this objection by providing a low watercontrol that is strongly resistant to sticking and which will cause themakeup water valve to open if it sticks. This is desirable because theboiler cannot then be injured -because of false indications of the lowwater control. It isttherefore an object of lthe present invention toprovide a low water control that is Astrongly resistant to sticking andwhich will energize the makeup water valve if it does stick.

The present invention makes this possible by utilizing a light-sensitivecell in the low water control, and by using a float in the water gage.of the boiler to selectively intercept light directed toward that cell.If the level of the water in the boiler becomes low enough for the floatto intercept the light to the light-sensitive cell, that cell willenergize the makeup water valve and assureV replenishment of the waterin thefboiler. The float will be strongly resistant to sticking and willonly stick in the water gage if the sludge in the boiler becomesexcessive. However, before the sludge in the boiler can become heavyenough `to make the float stick, that sludge will render the water inthe water gage opaque andl will cause the makeup water valve to open andintroduce freshwater into the boiler. The introduction of. the freshwater will veither dilute the sludge in the boiler to the extent thatthe water in the water gage become transparent or the water from themakeup water valve will till the boiler and preventI further generationof steam. The consequent cooling of the area being heated will lead toprompt investigation and prompt cleaningV of theA boiler. lnk eitherevent, the boiler will be protected against damage. It is therefore anvobject of the` present invention toprovide al low water control whichhas a*y light-sensitive cell adjacent the water `gage of a boiler andwhich has a float to selectively interassure safe opcept light directedtoward that cell as the level Iof the water in the boiler varies.

The control provided by the present invention has a light-sensitive cellto control the operation of the combustion apparatus, and that cell willshut off that apparatus if the water level in the boiler falls below apredetermined value. The light-sensitive cell that shuts off thecombustion apparatus is disposed below the light-sensitive cell thatcontrols the makeup Water valve. With this arrangement, theylight-sensitive cell that controls the makeup water valve will normallyassure the maintenance of an adequate supply of water for the boiler,but if for some reason that cell is not able to do so, the lowerlightsensitive cell will shut off the combustion apparatus. The floatthat can interrupt the light to the light-sensitive cells will be longenough so that when it is in register with the cell which can shut olfthe combustion apparatus, it will1 also intercept light to the cellwhich controls the makeup water valve. This is desirable since it willkeepl water flowing into the boiler and may make it possible for thecombustion apparatus to cycle again. However, if there is a serious leakin the boiler and the ply is unable to raise the level of the water inthe boiler sufficiently to raise the float, the owner of the boiler willbe assured that no explosion can occur.

Other and further objects and advantages of the present i inventionshould 'become apparent fromv an examination of the drawing andaccompanying description.

In the drawing and accompanying description, a preferred embodimentofthe present invention is shown and described but it is to beunderstood that the drawing and accompanying description are for thepurpose of illustration only and do not limit the'v invention and that'the invention will be defined by the appended claim;

In the drawing.

Fig. 1 i-s a schematic diagram of the control circuit provided by thepresent invention,

Fig. 2 is a view of the basic amplifier circuit and lightsensitive cellused therewith inthe control circuit of the present invention,

Fig. 3 is a front elevational view of a combustion head which can becontrolled by the circuit of the present invention,

Fig. 4 is a side elevational View ofy an electrically responsive makeupwater valve,

Fig. 5 is a partially sectioned side elevational View of a header andwater gage for a boiler and of light sourcesand light-sensitive cellsused with that water gage, and

Fig. 6 is a sectional view of the water gage and one light source andlight-sensitive cell of Fig. 5.

Referring to the drawing in detail, the numerals 10 and 12 denote theterminals of a preferred form of control circuit provided by the presentinvention. These terminals can be connected to a suitable source ofelectricity, as for example, one hundred and fifteen volts alternatingcurrent. The terminals are connected toa main switch that has contacts14 and 16. This switch will preferably be manually operated and when itis operated', the circuit is completely disconnected from the source' ofelectricity. Two fuses 18 and 20 are connected in the lines' extendingfrom the contacts 14 and 16 of the main switch. A switch 22 is providedwhich will open whenever the level of the water in the boiler or otherheat absorbing device falls rbelow a predetermined value. This switchwill preferably be electrically responsive and will automaticallyoperate whenever the level of the falls too far. A fuel pressure switch24 is provided that' will respond to decreases in the pressure of thefuel supply to open the circuit. This switch will be' apressureresponsive switch of standard design and willV have thepressure-responsive portion thereof inj communication y with the fuelsupplied to the combustion-apparatus under makeupwater sup-v water inthe boiler 200'A 3 the control of the circuit provided `by the present`invention. A lead extends from the switch 24- to a scanner 26 which isshown in detail in Fig. 2. rlie lead 27 extends rom the fuse 18 to thatscanner. Two leads 29j and 31 extend from the scanner 26, and the lead29 is directly connected to the lead 25 at the junction 23 within the`scanner 26. A junction 28 is provided in the lead 29 and a junction `30is provided in the lead 31. These junctions connect the coil 32 of arelay across the leads 29 and 31.` That relay has an armature 34 withspaced contactors 42 and 44 thereon. The contactor is movable bythe'coil 32 into engagement with the spaced contacts 36 of that relay,and the contacter 44 is movable to selectively bridge the spacedcontacts 40 and the spaced contacts 3S. The armature 34 will normally bein the i position shown in Fig. l and will hold the contacter 44 inbridging relation tothe spaced contacts 4, but will respond toenergization of the coil 32 to move the contactor 44 into bridgingrelation with the spaced contacts 38 and will move the contacter 42simultaneously into bridging engagement with the spaced contacts 36. Theupper contact 36 `is connected to the fuse 18 `by the junction 35 andthe upper contact 38 is connected to the fuse 18 by the junction 37.`

The primary winding 46 of a transformer is connected between the lowercontact 40 of the relay and a junction 92 in the conductor 29. Thesecondary winding 48 of that transformer has one end thereof connectedto one of two spaced electrodes 50 and has the other end connected tothe other of those spaced electrodes by the coil 52 of a sensitive relayand bythe lead 51. The armature 62 yof the relay carries contactors 58and `6), andA the contactor 58 selectively bridges spacedcontacts 54 andcontactor 60 selectively. bridges `spaced contacts 56. When the coil 52isenergized the armature 62 will move upwardly and cause the contactors58 and 60 to bridge the spaced contacts 54 and 56 respectively.` Theright hand contact 54 is connected to the fuse 18 by way of junctions55, 53, 35 .and .37; and the right hand contact 56 is connected to thefuse 18 by the junctions 55, 53, 35 and.37.` The lefthand contact 54 isconnected to an electrically responsive valve 64 and through that valveto the junction 92 in the lead 29. The valve 64 is the starting pilotvalve. The lefthand contact 56 is connected by a junction 67 to a relay68 for the blower motor of the pilot. The other side of the relay 68 isconnected to the junction 92 in the lead 29.` The bottom contact 38 isconnected to an electrically responsive valve 66 4which has the otherterminal thereof connected to the junction 92 in the lead 29. The valve66 is the running pilot valve and supplies fuel to the pilot nozzleduring running conditions. The Contact 36 of the relay which has thecoil 32 is connected through the junction 67 to the relay coil 68.

A manually set main fuel valve, which is commercially available, isdenoted by the numeral '70, and one terminal thereof is connected to thelead 31 by way of the junctions 69 and 30. The other` terminal of thatvalve is connected to the lead 29 at the` junction 92.` A low lireblower relay for a blower motor is denoted by the numeral 74 and oneterminal of that relay is connected to the junction 92 of lead 29. i Theother terminal of that relay is selectively connected to the junction 69of the lead 31 by a normally open steam pressure switch 72. This switchwill preferably be a steam pressure-operated switch commercially knownand available as a Pressuretrol switch. An electrically responsive lowtire main fuel valve 78 is connected to the junction 92 of lead 29 andis; selectively connected to the junction 69 of the lead31 by theswitches 72 `and 76. The switch 76 is an air-pressure switch that willrespond to air pressure generated by the blower controlled by the relay74. A high re blower relay 82 which controls the blower of still anothernozzle of the combustion apparatus with which the present control is`used is denoted by the numeral 82. One terminal of this relay isconnected to the junction 92 lil of lead 29 and the other terminal isconnected to the junction 69 of the lead 31 through the switches 72, 76and 80. The switch will preferably be a steam pressure-operated switchwhich is commercially known and available as a Pressuretrol switch. Anair pressure switch 84 extends between the switch 80 and the switch 86,and the switch 84 is an air-pressure switch which will be operated bythe air-pressure from the blower controlled by the relay 82. The switch86 is a thermally responsive switch that is controlled by temperaturesexteriorly of the building being heated by the combustion apparatus. Theswitch 86 is normally in the position shown but will automatically shiftto its other contact in periods of abnormally cold weather. The numeral88 denotes an electrically responsive valve for the regularly used fuelof the combustion apparatus, and it is referred to as the regular mainfuel valve; and the numeral 90 denotes an electrically responsive valvefor the alternatively used fuel of that combustion apparatus, and it isreferred to as the alternate main fuel valve.

The scanner includes a primary winding 94 of a transformer, and thatwinding is connected to the leads 2S and 27. A low voltage secondarywinding 96 is provided for the transformer, and that Winding suppliesthe current for the lament of a triode 100.` A high voltage sec ondarywinding 98 is provided for that transformer, and one end of that windingis connected to a condenser 108. The condenser 1081is connected to thegrid of the triode 100 through a grid leak 106 and is also connected tothe cathode of a light-sensitive cell 110. The anode of thelight-sensitive cell is connected to a tap 111 on the high voltagesecondary winding 98. The cathode of the triode 100 is connected to atap 102 on the high voltage secondary winding 98. A lead 104 connectsthe cathode to oneside of the filament of the triode 100. The plate ofthe triode 100 is connected to the other end of the high voltagesecondary winding 98 through a relay 112 and a resistor 114.` Acondenser 11.6 is connected in parallel with the serially-connectedrelay 112 and resistor 114. The relay 112 has an armature 118 thatresponds to energization of the relay 112 to connect the lead 31 withthe lead 27. The triode 100, the light-sensitive cell and thecondensers, resistors and relay associated there with constitute ascanner which can shut off the combustion apparatus whenever the flameof the combustion apparatus is extinguished However, that scanner willpermit operation of the combustion apparatus under the control of thesteam pressure-operated switches whenever the light-sensitive cell 110sees a flame.

When the contacts 14 and 16 of the main switch arc closed, current willow through the primary winding 94 if the normally-closed switches 22 and24 are closed. This current will cause the secondary Winding 96 to heatthe iilament of triode 100, and will cause the upper end of thesecondary winding 98 to become successively` positive and negative withrespect to the lower end of that winding. During the positive halfcycles, when the upper end of winding 98 is positive relative to thelower end of that winding, the grid of triode 100 will be more positivethan the cathode of that triode; and grid current will flow. This gridcurrent will create a voltage drop across the resistor 106 that willbias the` triode to cut ott; and condenser 108 will maintain that biasand prevent the flow of plate current during the negative half cycleswhen the upper end of winding 98 is negative relative to the lower endof that winding. Grid current will again ow on the succeeding positivehalf cycles, and if any of the grid bias is lost during the negativehalf cycles because of leakage through the condenser 108, the ow of gridcurrent on the positive half cycles will restore the grid bias.Accordingly, until the light-sensitive cell 110 sees a flame, the triode`100 will be biased to cut off and no plate current will flow toenergize relay 112.

When the lght-sensitive cell 110 sees a arne, that cell will conductcurrent on the negative half cycles, and

the current flowing through the cell 110 will discharge condenser 10.8and thus reduce the bias on the grid ofv triode 100 to ,a value thatwill permit plate current to llow through triode 100; That plate currentwill energize the relay 112 and pull the armature 11,8'intocircuitclosing position. The plate current will also charge condenser116 to the value of thevoltage drop across relay 112 and resistor 114,and on the positive half cycles that condenser will partially dischargethrough that relay and resistor and keep the relay 112 energized. Thetime constant of condenser 116 and resistor 114 will be great enough tomaintain an energizing current flow through relay 112 until the platecurrent again flows in the next negative half cycle. Hence, as long asthe light-sensitive cell 110 sees a llame, the relay 112 will be keptvenergized and armature 118 will be held in closed circuit position.However, when the cell 110 fails to see a llame it will be unable toconduct current, and a bias will be generated on the next positive halfcycle that will bias the triode 100 to cut olf. Thereupon the relay 112will become de-energized, and armature 1'18 will move to circuit-openingposition.

The numeral 120 denotes a cylinder which is' part of a combustion headfor combustion apparatus such as is shown in my application forCombustion Apparatus, which was filed May 1, 1953, and which 'bearsSerial No. 352,498. That cylinder has an opening in one side thereof anda tube 122 is secured to the cylinder adjacent that opening. The tube122 may be secured to the cylinder 120 by welding or other suitablemeans. The scanner 26 is mounted on the outer end of the tube 122 andthe light-sensitive cell 110 is in register with the tube 122.Consequently, the llame which is vcreated by the combustion head `ofwhich the cylinder 120 is a part can be seen by the light-sensitive cell110, The cylinderl 120 cooperates with a cylinder 124 to deine a nozzlefor high lire air, and the cylinder'124 coacts with a cylinder 126 todefine a nozzle for the pre-mixed gas and air of the high lire. Thecylinder 124 has an inwardly directed ilange at the end thereof whichcoacts with the exterior of the cylinder 126 to define a nozzle ofpredetermined' cross-section. The tube or cylinder 126 has an inwardlydirected ange which coacts with the exterior of a cylinder 128 to definea nozzle for the premixed gas and air of the low fire provided by thecombustion' head. The cylinder 128 cooperates with the pilot nozzle 130to dene a nozzle for low re air. A nozzle for uid fuel, such as `oil orpowdered coal, is disposed in the center of the pilot nozzle 130, and itis denoted by the numeral 132. Suitable pipes and ducts, not shown, areprovided to supply gas to the low lire, high fire and pilot nozzles andto supply oil or powdered coal to the nozzle 132. The combustion headdisclosed in Fig. 3 is an efficient and effective source of heat, butthe control provided by the present invention could be used with othercombustion heads, andthe combustion head of Fig'. 3 is for illustrativepurposes primarily.

A rod 134 of stainless steel or other corrosion resistant metal extendsthrough the wall of the cylinder 12) and extends adjacent the pilotnozzle, the low re nozzle and the high lire nozzle. The rod 134 isvsupported by a mounting 136 which is carried by the exterior of thecylinder 120. The rod 134 will act as a` llame rod and will respond toeither the pilot, the' low tire or the high re to become hot enough toevolve light. In addition, that llame rod will cause the products' ofcombustion which are adjacent that rod to assume a characteristic orangecolor. Where the pilot nozzle alone is operating, the innermost end ofthe ame rod 134 will become red and the pilot flame will assume thecharacteristic orange color. When the low fire is burning the rod 134will have a section of red heat that is as long as the combined lengthof the rodv in the pilot llame and'in lthe low re llame. Both the pilotand low lire flames willv have the characteristic orange color; Whenthehigh ltire is` f the pilot nozzle 130 and which can 'cell 170.Moreover,

also operating, the red hotsection of the rod 134 will extend from `thepilot flame through the low lire flame to the high lire flame, and allthree ames will assume the characteristic orange color. the combustionhead so it is in register with the lightsensitive cell throughout the'portion that will be heated to a red heat by the three llames. Moreover,the portions of those llames which are adjacent the llame rod 134 willalso be in visual communication with the light-sensitive cell 110;. As aresult, the cell 110 will see a llame of distinctive orange color andwill see a red hot llame rod whenever the pilot or the low tire or thehigh lire is operating. The presence of the llame rod is desirable fortwo reasons; rst, it makes certain that when a llame is in thecombustion head it will provide a visible target for the light-sensitivecell 110 irrespective of the color or composition of the flame, andsecond it will convert the llame to` a characteristic and distinctivecolor that will be constant irrespective of variations in pressure andlargely irrespective of changes in the composition of the fuel.

The numeral 138 denotes insulators which extend through openings in thewall ofthe cylinder 120. These insulators carry the electrodes 50 whichextend toward draw an arc between them to ignite the pilot. Theinsulators 138 are sealed to the cylinder by mounting seals 140, andleads 49 and 51 are connected to the electrodes Sil.

The numeral 142 denotes a line which extends between a source of water,such as a water main, and the boiler or other heat absorbing device 200.This line will provide' make-up water for the boiler or other heatabsorbing device. An electrically responsive valve 144 is provided intheline 142, and that valve is spring biased to open position. Whenevercurrent flows through the ycoil of the valve 144, that valve will closeand halt further introduction of make-up water into the boiler or otherheat absorbing device.

The numeral 146 denotes a header for the boiler 200 and that header hasan L extending toward the boiler, and it has a nipple the L beingdenoted by the numeral 148 and the nipple being denoted by the numeral150. The L 148 is suitably connected to the boiler 200 by piping 202,and the nipple 150 is suitably connected to the boiler 200 by piping204. A number of drain lcocks are denoted by the numeral 152, and thosedrain cocks are mounted ron the side of the header 146. The header 146,the L 148, the nipple 150, and the drain cocks 152 are of standard andusual design. A water gage 154 is supported by the header 146 throughthe medium of shut olf valves 156 and nipples 158. The nipples 158 andthe shut olf Valves 156 selectively place the water gage 154 incommunication with the water in the boiler. A drain cock 160 is providedat the bottom of the lower shut olf valve 156 to facilitate draining ofthe water gage 154.

A hood 164 is mounted adjacent the water gage 154 and that hood containslight sources 166 and 168. These light sources can be luorescent lampsor incandescent lamps or other customary and well known sources oflight. and they each direct light through the water gage 154 and thewater therein. A light-sensitive cell 170 is disposed on the oppositeside of the water gage 154 from the light source 166 and it is inregister with that light source. A light-sensitive cell 172 is disposedon the opposite side of the water gage 154 from the light source 168 andit is in register with the light source 168. A hood 174 encases thelight-sensitive cells 170 and 171 is disposed between those cells. Abaille 167 is disposed between the light sources 166 and 168. The bales167 and 171 and the two hoods, 164 and 174, keep the light from thesource 166 from striking the cell 172 and keep the light from the source168 from striking the The rod 134 is disposed in The source 166 isdisposed above the source 168 172; and a baille,

those hoods keep light from .other sources from striking the cells 170and 172. A float 176 of opaque material, such as a hollow metalfloat, ismounted Within the water gage 154. The tloat has axially directed andradially extending projections 178 thereon to minimize the contactbetween the float 176 and the interior of the water gage 154. Moreover,those projections tend to reduce the effect that surface tension orcapillary action could have in restricting movement of the float withinthe water gage 154. A stop 180, in the form of a section of tubing, ismounted within the water gage 154. The top of the tubing 1&0 is adjacentthe bottom of the hood 164, and it will keep the float 176 from movingdownwardly below and out of register with the light-sensitive cell 172.

The light-sensitive cells 170 and 172 will bc similar to thelight-sensitive cell 1.10ct Fig. 2. Moreover, those light-sensitivecells will be `.connected in amplifying circuits similar to thatdisclosed in Fig. 2. However, the transfoirners in those amplifyingcircuits will be connected directly to a source of electricityV by leads208 and 206 respectively and will not be connected through the mainswitch contacts14 and 16. As a result, the light sources 166 and 16Swill be on throughout the twenty-four hours of the day. The amplifyingcircuit which is connected to the light-sensitive cell 170 by leads 210is indicated by the box 212 in Fig. 4; and it will not have a relay suchas the relay 112 but instead will have the coil of theelectrically-responsive valve 144 connected between the plate of thetriode and the resistor of the resistor-capacitance network. Thus;whenever light reaches the lightsensitive cell 170, the valve 144 willbe energized to closed position to halt the introduction of make-upwater into the boiler. If the tioat' 176 intercepts the light from the.source 166 or if the sludge in the boiler 200 discolors the water in thewater gage 154 sufficiently, light will no longer be able to reach thelight-sensitive cell'170 and thereupon the triode will be biased tocutoff and the spring bias of the valve 144 will open that valve andpermit make-up water to enter the boiler. rThe amplifying circuitconnected to the light-sensitive cell 172 by leads 214 is indicated bythe box 216 in Fig. 1; and it will have `a relayicoil similar to therelay coil 112, but that relay coil will be adjacent the switch 22 ofFig. l.` The switchr 22 will be biased to open positionbut `will bepulled into closed position whenever the light from source 168 strikesthe light-sensitive cell 172. If the oat 176 ever intercepts the lightfrom the source 16S, or if the sludge in the boiler colors the water inthe water gage 154 sufficiently, the bias on the grid of the triode `inthe arnplifying circuit for the cell 172 will `be great enough toprevent the ow of current through the relay controlling the switch 22;and thereupon the spring bias on that, switch Willcause it to open andshut olf the control.

It will be noted that the float 176 is long enough that it wiilintercept the light to both of the cells 170 and 172. This is desirablesince it will enable the control of the present invention to continue`to pass make-up water into the boiler when the control shuts off theburner. As a result, there is a possibility that a self-healing break ina water tube or tire tube could permit the control to continue tooperate safely after the water level had been raised suiciently. Thestop 181i will keep the float 176 from moving below and out of registerwith the cell 172; and this is desirable since any such movement of thefloat 176 would restore the light to 172 even though the water level wastoo low.

in the operation of the control provided by the pres ent invention, theswitches 22 and 24 are normally closed; the switch 22 being held closedby the amplifying circuit connected with the light-sensitive cell 172,and the switch 24 being held closed by the pressure of the fuel used inthe combustion apparatus withwhich the control is operated. When themaster contacts 14 and 16 are closed, current will flow from theterminal through switch contact .14, through fuse 18, across the bridgedcontacts 40, through the primary winding 46, through junction 92,through junction 28 and through the lead 29 to the junction 23 and .thenthrough the lead 25' to the switches 24 and 22 and finally throughthefuse 20, and switch `contact 16 to the terminal 12. In addition, currentwill flow from the terminal 10 through the switch contact 14 through thefuse 18, past the junctions 37, 35, and 53, through the` primary winding94, past the junction 23 and through the switches 24 and 22, through thefuse 2i) and through the switch contact 16 to the terminal 12. Thepassage of the alternating current through the primary windings 46 and94 will energize the secondary windings 48 and 98. No current will flowin the triode plate circuit connected to the secondary winding 98because the triode will be biased to cut off since the light-sensitivecell 11i) sees no llame. The ow of current in the secondary winding 48will cause an arc to span a gap between the electrodes 50 and the arcwill complete the circuit through the relay coil 52. This relay is avery sensitive `relay and will respond to that current flow to move thearmature 62 and bridge the spaced contacts 54 and 56. Thereupon, currentwill flow from the tert minal 10 past contact 14, past fuse 18, pastjunctions 37, 35, and 53 to junction 55; and the current will then oweither past the bridged contacts 54 or past the bridged contacts 56. Thecurrent flowing past the bridged contacts 54 will pass through thestarting pilot valve 64 to the junction 92 and the current flowing pastthe bridged contacts 56 will pass through the relay 68 which controlsthe blower for the pilot. The current will unite at the junction 92 andow past the junction 28 and past the junction 23 to the lead 25 and thensuccessively past the switches 24 and 22, the fuse 20 and the switchcontact 16 Vto the terminal 12. It Will be noted that until the currentspanned the gap to establish an arc, that the valve 64 was closed andthat the valves 66, 70, 78 and 38 were also closed. Hence, no fuel couldbe introduced into the combustion head until after the spark had proveditself, and then the only fuel that could be introduced into thecombustion head was the fuel for the starting pilot. The fuel from thevalve 64 will mix with the air from the blower controlled by the coil 68and will be discharged from the pilot nozzle 130. This fuel and air willbe ignited by the arc between the electrodes` 50 and the resultingflamewill heat the flame rod 134. The ame rodwill become red hot andwill also provide a characteristic orange color for the pilot fiame; andthe lightsensitive cell will see both the red hot portion of the rod 134and the ycharacteristically colored portion oi the flame surroundingthat rod. Thereupon, the negative bias on the grid of the triode 100will be reduced to the point where the triode can conduct current andthereupon the relay 112 will close the switch 118. The closing of theswitch 118 will establish a circuit from the terminal 10 through contact14 through fuse 18, past junctions 37 and 35 and 53, through the switch118, past the junction 30,` through the relay coil 32, past the junction28, past the junction 23 and through the switches 24 and 22, through thefuse 20 and through the contact 16 to the terminal 12. This flow ofcurrent energizes the solenoid coil 32 and moves the armature 34 to theright where it causes the contactor 44 to bridge the spaced contacts 3Sand causes the contacter 42 to bridge the spaced contacts 36. As thearmature 34 moved, it broke the circuit through the primary winding 46and thus interrupted the spark between the electrodes 50. However, thepilot ame from the nozzle will supply the llame necessary to ignite thefuel from the other nozzles of the combustion head. When the contactor44 was moved out of engagement with the spaced contacts 40, the relay 52was deenergized and the circuit to the starting pilot valve 64 and thecircuits to the relay for the pilot blower motor were interrupted.However, almost simultaneously, the

.circuit to the running pilot valve 66 was established through thebridging of the spaced contacts 38 and the einem eireuit te the relay 68whielieemrele the Pilet blauer tor was established through the spacedIcontacts 361'. In' the rst instance the current flows from the' terminal10r through the contact 14, through the fuse 18, past the junction 37,through the contacts 38 and the contactor 44, through the running pilotvalve 66. peet the junctions 92.. 28' and 23 to the switches 2 4 and' 22' and then through the fuse v and the contact 16 to the terminal 12, Inthe second case the circuit extends' from the terminal` 10 past thecontact 14, past the fuse 18, past ythe junctions 37 and 35, through thecontacts 36 and the contacter 42, past junction 67 and through the relay68 which controls the pilot blower motor, past the junctions' 92, 2 8,and 2 3 to the switches 24 and 22 and then through the f use 20 andthecontact 16 to the terminal 1 2, Immediately, and without anyquenching of the pilot flame the shift from the Starring pilot valvetothe running, alle? valve .is made, and the flame rod 134' willyretain" itfsf redf heat' and the flame will retain its characteristic;orange color.

If the pilot llame were to become extinguished, the ylightsensitive cell110vwould, no longer see a haine andthe triode 100 would immediately be.biased to cut oif and the switch 118 would open. This would deenergizethe relay coil 32 and thereupon the circuit to the running pilot valveand to the relay for the pilot blower motor wouldbe interrupted at thespaced contacts 38`and 3 6 respectively.r

Simultaneously, the circuit to the primary winding 46 would be restoredby the contactor 44, and-"the arc would again be proved. The valve 6.4would again be opened and the relay 68 would again be energized bymovement` of the armature 62 o f the sensitive relay 52, and the pilotwould again be ignited and the flame vrod 134 heated `to red heat. Thescanner 2 6 would then reenergize the running pilot valve 66 andreenergize the relay 6 8 for the pilot blower motor while alsodeenergizing'the circuit. o f the electrodes 50 and the sensitive relay52.l Thus, the present invention fully proves the spark before itpermits any fuel to enter the combustion. head, andV it monitors thepilot and shuts olf the fuel to the piiotif the pilot becomesextinguished. Moreover, the present invention automatically recycles theigniter for the pilot until the pilot llamey proves on the scanner.v

Once the running pilot flame-has been established and proved, the valve70 can be operated. This valve, which is commercially known andavailable, has" a handle which is operated manually but which willremain in moved position only if current hows-throughthe`electromagnetic coil of that 'va-lve. Thus, until the circuit throughvthe valve 70 is completedat the switch 118 in the amplifier circuit ofthe scanner, the valve 70 cannot be kept on Once the pilot ame hasbeeneestablished and then proved by the scanner, however, the valve 70can be kept on The valve 70 is connected between the source of fuel andthe fuel valves 78 and 88 and it will automatically close and stopfurther flow of fuel to valves 78 and 88 if the scanner 26 does not seea ame in the combustion head; however as long as the pilot flamecontinues, the valve 70 will permit the ow of fuel to the valves 78 and88.

If the boiler or other heat absorbing device requires additional heat,the switch 72 will close and energize the relay 74 which controls theblower for the low fire. After that low lire blower has created apredetermined air pressure in the duct leading to the secondary airnozzle for the low re, the switch 76 will close and energize the valve78. This valve supplies the fuel for the low lire. If the heat providedby the low tire is suflicient to meet the needs of the boiler or otherheat absorbing device, the low tire will continue to supply heat untilthe needs of the boiler or other heat absorbing device are met and thenthe switch 72 will open. Thereupon the relay 74 and the valve 78 will bede-energized, and the low tire will be extinguished.

If the low fire was unable to provide the heat required by the boiler orother heat-absorbiug device, the switch 10 would loseand energize therelay 82 which controls thehlowerrnotor'for the-highfhe Astheblower'motor for the high hre starts to operate, it willA increase thepressure'ny the air duct tothe secondary air nozzle for the high fireand will close the switch 84; and thereupon either the valve'88 or 90will open, the particular valve being opened being dependent upon theposition of the thermally responsive` switch 86; In either event thefuel from the valvev 88 or the valve'9`0` will mix with the air from theblower controlled by the relay 82, and the resulting mixture will ignitefrom the pilot or from .the low lire. The

resulting llame will be the high lire of the combustion head. If thetemperature exteriorly of the area being heated by the boiler or otherheat absorbing device is above a predetermined value, the closing of theswitch 84 will energize the valve 88, but if that temperature is belowthat predetermined value, the closing of the switch 84 will energize thevalve 90. The secondary air and the fuel ofthe high lire will continueto supply heat to the boiler or' other heat absorbing device until theswitch 80 opens. Thereupon the relay 8 2 and the valve 88 or 90 will bedeenergized- It'will be noted that the high lire fuel and air can not besupplied to the combustion head until after the low re fuel and air arebeing supplied to that combustion head, because the switches 72 and 76are intermediate the terminals 10 and 12 and the switches 80 and 84. Inone particular embodiment of the present invention the switch 72 was set'so it closed when the pressure of the steam in the boiler was seventypounds and so it opened when the steam pressure exceeded eighty pounds,and so the switch 80 closed when the steam pressure fell to sixty eightpounds and opened when that pressure reached seventy ve pounds. Thearrangement used in the said embodiment enabled the control provided bythe present invention to closely match the needs of the boiler with'-out any overshooting.

The fuel from the valves 64 and 66 will support the pilot, the fuel fromthe valve 78 will support the low re, and the fuel from the valves 88and 90 will selectively support the high lire. In each case the ameswill envelope portions of the llame rod and heat those portions to a redheat and also cause that llame rod to give the flames the characteristicorange color. rl`.he light-sensitive cell will continuously monitor theflames in the combustionn head, and the light-sensitive cells and 172will continuously monitor the level of .the water in the boiler. In thisway, full and complete protection is afforded to the boiler and to thepersonnel working with that boiler; If thelight-sensitive cell 110 failsto see a flame it will open the circuit of the valve 70 at the switch118 and thereafter the switch 78 will have to be re-closed by hand. Thismakes certain that the cause of the extinction of the pilot, low iireand high tire flames will be investigated before the low lire and highlire tiames can be reeestablished. The pilot will automatically bere-established if a spark can be drawn between electrodes 5G, and there-establishment of the pilot is desirable since it will enable thatpilot to burn any fuel that might be leaking past any of the valves 70,78, 88 or 90. Even the best valves can leak if pipe scale or otherforeign material lodges between the seat of the valve and the movableelement of the valve.

In some instances it may be desirable to use a glow plug instead ofspark plugs, such as the spark plugs 50. In those instances the step-uptransformer of Fig. 1 will be replaced with a step-down transformer, andthe spark plugs will be replaced by a glow plug. Current flowing throughthe primary winding of the step-down transformer will cause current toow through the secondary 'winding of that transformer and thus throughthe glow plug and the coil S2. As long as the glow plug is in goodcondition, it will conduct current in sufficient quantities to energizethe coil 52; but if that glow plug burns out or otherwise fails to passits normal current, the coil 52 will be unable fi1 f to hold thearmature 62 in position to bridge the spaced contacts 54 and 56. Whetherthe glow plug or the sparkv t plugs are used, the coil 52 can not beenergized' properly unless the igniter, in the form of the glow plug orthe spark plugs, can pass the required current for the said coil.

Whereas a preferred embodiment of the present invention has been shownand described in the` drawing and accompanying description, it should beapparent to those skilled in the art that various changes may be made inthe form of the invention without affecting the scope thereof.

What I claim is:

In combustion apparatus that heats liquid `in a boiler, a control thatcomprises a transparent casing connected to and in communication withsaid boiler, an opaque float disposed within said casing for verticalmovements therein, a water line connected to said boiler to supplymake-up water thereto, an electrically responsive valve incorporated insaid make-up water `line that is biased to open position but is normallyheld closed by the energization thereof, a light-sensitive cell that isadjacent said casing and that is positioned to receive light passingthrough said casing, a fuel line connected to said combustion apparatusto supply fuel thereto, a second electrically responsive valve that isincorporated in said fuel line and that is biased to closed position butcan be energized to open and permit the flow of fuel to said combustionapparatus, a second light-sensitive cell that is adjacent said casingand that is positioned to receive light passing through said casing, asource of light that is adjacent said casing and that is aligned withthe first said light-sensitive cell, a second source of light that isadjacent said casing and that is aligned withisaid secondlight-sensitive cell, the iirst said and said second light sensitivecells `normally receiving light that is emitted by the lirst said andsaid second sources of light respectively and that passes through saidcasing, the first said light-sensitive cell being positioned above thelevel of said second light-sensitive cell, a baiiie intermediate saidlight-sensitive cells to isolate each of said light-sensitive cells fromthe light intended for` the other of said cells, said opaque float beingmovable into position intermediate the tirst said light source and theirst said light-sensi tive cell to intercept the ,light that is emittedby the iirst said light source and normally passes through said casingto the first said light-sensitive cell, said opaque `iioat being movableinto position intermediate said second source `ot light and said secondlightsensitive cell to intercept the light that is emitted bysaid secondsource of light and normally passes to said second lightsensitive cell,said opaque tloat being longer than the spacing between saidlight-sensitive cells whereby said float can 12 t simultaneouslyintercept the light that normally passes to both of said light-sensitivecells, a stop that prevents said oat from moving down to a positionwhere it would be wholly below the level of said second light-sensitivecell, a circuit that responds to interruptions in the light normallyreceived by the first said light-sensitive cell to de-energize, and thusopen, the rst said electrically responsive valve and that responds torestoration of the light received by the first said light-sensitive cellto energize, and thus etect the closing of, the first said electricallyresponsive valve, and a circuit that responds to the light received bysaid second light-responsive cell to energize, and thereby open, saidsecond electrically responsive valve to permit the ow of fuel to saidcombustion apparatus and that responds to interruptions of the lightreceived by said second light-responsive cell to de-energize, and permitthe closing of, `said second electrically responsive valve, said casingbeing long enough to permit said tloat to move to an upper positionwholly above the level of the first said light-sensitive cell, saidlloat responding to the water level in said boiler, and hence in saidcasing, to move to said upper position to permit both of saidlightsensitive cells to receive light and thereby energize the firstsaid electrically responsive valve and to energize said secondelectrically responsive valve, said iioat responding to a lower Waterlevel to move to an intermediate position to intercept light normallyreceived by the rst said light-sensitive cell and thereby die-energizeand open the rst said electrically responsive valve while permittingsaid second light-sensitive cell to receive light from said secondsource of light and hold said second electrically responsive valveenergized, said float responding to a still lower water level tointercept the light normally received byboth of said light-sensitivecells to de-energize both said electrically responsive valves, therebysupplying make-up water while shutting olf the supply of fuel.

References Cited in the tile of this patent UNITED STATES PATENTS352,647 Chegan Nov. I6, 1886 1,840,744 Scott Ian. 12, 1932 2,078,479Briggs Apr. 27, 1937 2,091,303 Brelsford Aug. 3l, 1937 2,127,445Hardgrove Aug. 16. ,1938, 2,210,852 Falkenberg Aug. 6, 1940 2,335,655Dickey Nov. 30, 1943 2,362,045 Bliss Nov. 7, 1944 2,418,845 Long Apr.15, 1947 2,579,883 Thomson Dec. 25, 1951 FOREIGN PATENTS 600,450 GreatBritain Apr. 8, 1948

